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The authors evaluated the durability of current zeolite-type SCR (Selective Catalytic Reduction) catalyst system in terms of poisoning from engine oil components, such as phosphorus, sulfur, calcium and zinc. The engine oil types used included typical CF-4, a sulfur-free type and an ultra-high SAPS (Sulfated Ash, Phosphorus and Sulfur) type, etc. After 500 hours' engine operation with these oils, the NOx conversion rates were measured and compared. The test revealed no serious deactivation of the catalysts, but we observed some trends concerning the poisoning and its effects on the catalysts' activity. We also analyzed the contaminants on the catalysts and studied their effects.

In order to meet the increasingly tough emission regulations on diesel vehicles, automobile manufacturers in Japan are focusing on the development of diesel particulate filters (DPFs), nitrogen-oxide-reducing catalysts so-called deNOx catalysts, and other technology for reducing exhaust gases. In order to reduce catalyst poisoning, diesel fuel with a sulfur content of 50 ppm or lower-one-tenth the previous level-was put on the market in Japan in April 2003. At the same time, guidelines took effect for the new DH-2 and DL-1 standards for diesel engine oils compatible with after-treatment devices; the full regulations are scheduled to come into force in 2005. The newly developed low-ash diesel engine oil described here contains a reduced amount of metallic detergents, thus lowering the sulfated ash content to about two-thirds that of conventional high-ash oil.

In this study, the oxidation stability, soot dispersancy, antiwear performance, and friction-reducing capability of friction modifiers (FMs) were evaluated, and an SAE 5W-30 fully synthetic oil with MoDTC type FMs was developed for heavy-duty diesel engines. In several engine tests, it was confirmed that the developed oil can double the oil drain interval in comparison with API CD SAE 30, even when EGR is applied, and improves the fuel efficiency.